Abstract

The atomic structure of Al{sub 90}Sm{sub 10} metallic glass is studied using molecular dynamics simulations. By performing a long sub-T{sub g} annealing, we developed a glass model closer to the experiments than the models prepared by continuous cooling. Using the cluster alignment method, we found that “3661” cluster is the dominating short-range order in the glass samples. The connection and arrangement of “3661” clusters, which define the medium-range order in the system, are enhanced significantly in the sub-T{sub g} annealed sample as compared with the fast cooled glass samples. Unlike some strong binary glass formers such as Cu{sub 64.5}Zr{sub 35.5}, the clusters representing the short-range order do not form an interconnected interpenetrating network in Al{sub 90}Sm{sub 10,} which has only marginal glass formability.

@article{osti_22597854,
title = {Cooling rate dependence of structural order in Al{sub 90}Sm{sub 10} metallic glass},
author = {Sun, Yang and Ames Laboratory, US Department of Energy, Ames, Iowa 50011 and Zhang, Yue and Zhang, Feng, E-mail: fzhang@ameslab.gov and Ye, Zhuo and Ding, Zejun and Wang, Cai-Zhuang and Department of Physics, Iowa State University, Ames, Iowa 50011 and Ho, Kai-Ming and Ames Laboratory, US Department of Energy, Ames, Iowa 50011 and Department of Physics, Iowa State University, Ames, Iowa 50011 and International Center for Quantum Design of Functional Materials},
abstractNote = {The atomic structure of Al{sub 90}Sm{sub 10} metallic glass is studied using molecular dynamics simulations. By performing a long sub-T{sub g} annealing, we developed a glass model closer to the experiments than the models prepared by continuous cooling. Using the cluster alignment method, we found that “3661” cluster is the dominating short-range order in the glass samples. The connection and arrangement of “3661” clusters, which define the medium-range order in the system, are enhanced significantly in the sub-T{sub g} annealed sample as compared with the fast cooled glass samples. Unlike some strong binary glass formers such as Cu{sub 64.5}Zr{sub 35.5}, the clusters representing the short-range order do not form an interconnected interpenetrating network in Al{sub 90}Sm{sub 10,} which has only marginal glass formability.},
doi = {10.1063/1.4955223},
journal = {Journal of Applied Physics},
number = 1,
volume = 120,
place = {United States},
year = 2016,
month = 7
}

Here, the atomic structure of Al 90Sm 10 metallic glass is studied using molecular dynamics simulations. By performing a long sub-T g annealing, we developed a glass model closer to the experiments than the models prepared by continuous cooling. Using the cluster alignment method, we found that “3661” cluster is the dominating short-range order in the glass samples. The connection and arrangement of “3661” clusters, which define the medium-range order in the system, are enhanced significantly in the sub-T g annealed sample as compared with the fast cooled glass samples. Unlike some strong binary glass formers such as Cu 64.5Zrmore »35.5, the clusters representing the short-range order do not form an interconnected interpenetrating network in Al 90Sm 10, which has only marginal glass formability.« less

Contrary to the cooling-rate induced hardening observed in crystalline metals, the authors report here an unexpected surface softening in rapidly solidified Zr{sub 50}Cu{sub 50} bulk metallic glass. A soft layer {approx}500 {micro}m thick was detected near the surface with both hardness and elastic modulus increasing from the surface to the interior. To understand the reason for this, a correlation between cooling rate and defect concentration was derived. Defect concentration was found to increase as the cooling rate increased, suggesting that surface softening may be the result of freezing-in of excess defects, induced by a faster cooling rate near the surfacemore » compared to the interior.« less

Small volumes of Pd{sub 44}Ni{sub 10}Cu{sub 26}P{sub 20} and Pd{sub 43.2}Ni{sub 8.8}Cu{sub 28}P{sub 20} were encapsulated in B{sub 2}O{sub 3} and thermally cycled between T{sub g}-60 deg. C and T{sub l}+60 deg. C, where T{sub g} and T{sub l} denote the alloys' glass transition and liquidus temperatures. After this thermal treatment, the critical cooling rates (CCRs) for glass formation can be lowered by an order of magnitude, resulting in a critical cooling rate significantly lower than that reported for any other glass forming alloy melt. These experiments demonstrate that the CCR is not constant but strongly dependent on the degreemore » of heterogeneous nucleation.« less